Summary

In the first 2 months of this year, Nigeria has had more confirmed cases of Lassa fever, a hemorrhagic disease that kills 20% to 30% of those it sickens, than in any previous year. As of 11 March, the toll from this rodent-borne virus stood at 365 confirmed cases, 16 of those among vulnerable health care workers, and 114 deaths. And those figures are widely considered an underestimate. As the government and its international partners scramble to set up isolation wards and deliver protective gear to health workers, researchers on three continents are racing to figure out what is driving the unprecedented outbreak and what it portends for the future. Is it simply better disease surveillance in the wake of Ebola, the similar but more deadly disease that began its rampage across West Africa in 2014? Has the virus changed in some way? Are there more of the rats that carry it, or are more rats infected with it? Or is another rat capable of spreading the virus as well? Considering how lethal Lassa fever is, shockingly little is known about it, experts say.